Hello, Marimo.

Do you know Marimo? Roundish, green, and mossy—this unique indoor plant is full of personality! Marimo moss balls are equally strange and charming, allowing them to grow in popularity as interesting house plants. Aquascapers and aquarium fanatics are no strangers to these fuzzy algae balls as they are both decor and filtration for fish tanks. Marimo moss balls are increasingly found at garden centers and online for use in home water gardens of all sizes.

What is Marimo?

Marimo is the Japanese word for “ball seaweed,” which should give you the hint that, despite the common moniker Marimo Moss Ball, it is not moss at all. It is a type of green algae, Aegagropila linnaei, usually found in Australia, Estonia, Scotland, Iceland, and Japan rolling around at the bottom of freshwater lakes. Marimos are solid algae, radiating from the center and weaving themselves into a dense ball that is incredibly slow growing. Marimos grow only a few centimeters a year, so purchase them at a size you like and they will provide low-maintenance enjoyment for many years to come.

Caring for Marimo Moss Balls

Caring for a Marimo moss ball is easy, with no daily effort and almost no maintenance beyond changing the water. A Marimo moss ball is a great first plant for children and self-proclaimed “Black Thumbs.”

Water

Marimos are aquatic plants and, therefore, they need to be submerged in water to survive. The water requires no special care like distilling, adding chemicals, or boiling. Tap water is just fine in most areas unless your water is undrinkable from the tap.

Keep the water at room temperature and change it every two weeks. Frankly, I probably change the water every four to six weeks and my Marimos are happy as clams. The bowl gets a bit slimy after that time and starts to look cloudy, so I take five minutes to wash it and get back to enjoying these low-maintenance plants.

How to Clean Your Marimo Moss Balls

First, remove them from the water and set them in a bowl.

Wash the bowl, rocks, and any decorative items with gentle dish soap and warm water. Use a sponge or nail brush to scrub the film off the inside of the bowl.

Rinse the Marimos under tepid, running water by gently squeezing out the water and allowing them to fill again.

Fill the bowl back up with water and add the Marimos. If you have squeezed out too much water they will float to the top. Eventually, they will saturate with water again and sink to the bottom.

Tip: Don’t squeeze them into the clean water if you want them to float. The water removed will make the bowl cloudy, and you will have to change it again.

Get the Lighting Right

Marimos usually grow on the floor of lakes, so they do not want direct sunlight. Normal household lighting is just fine. Keep them safe from bright light and they will stay healthy for years.

Propagating Marimo Moss Balls

That nice, round shape comes from rolling around on the bottom of a lake when they are in nature. The Marimo that you’ll adopt is most likely captive bred. Breeders will divide up larger balls into many small ones by pulling off chunks and rolling those into a ball shape. Many of the “nano” balls that are sold are made this way. It will take some time for the algae to restructure and grow back into a ball shape with threads radiating from the center. In the meantime, they look pretty much the same and are not harmed.

If you have a large or misshapen Marimo, you can divide it and roll it into balls. Remove the balls from the water occasionally and roll them gently between your palms. Eventually, they will look like velvety round moss balls.

Beware of Fake Marimo Moss Balls

A real Marimo moss ball will be solid algae throughout, with the growth pattern radiating from the center outwards. It will tear easily if you try, but should not simply fall apart in water.

As with all plants, only purchase a Marimo from trusted suppliers. There are many fake Marimos out there, from Styrofoam balls with artificial moss glued on to hair algae rolled into balls. Ask the supplier if the Marimo they are selling is Aegagropila linnaei, and where they got their supply. And be sure to only make purchases from suppliers who stand by their products so that you can return it if you realize that it is a fake.

Designing with Marimo Moss Balls

If you are looking for a fun garden therapy project that has almost no care requirements, then use marimos to create a modern living water garden! Here is a simple Marimo moss ball water garden that you can make in just a few minutes.

Materials

Make it!

First add decorative pebbles to a clean glass vase or fishbowl. The wider the vase, the larger the moss balls will look. The water and glass easily distorts the size of what is inside, so choose decorative elements and moss balls that are smaller than you think you need.

Fill the bowl with tepid water.

Add any decorative elements like branches, coral, ceramic fish, or seashells to the bowl. You could even add a miniature garden scene under water.

Now rinse the Marimos under running water but squeezing them gently. Roll them between your palms to keep a nice ball shape and add them to the bowl.

Hi Liza, the moss balls you mean? They have them at aquarium stores, florists and garden centers here in Vancouver. I get them at GardenWorks sometimes. They also have them on Amazon and will either ship to Canada or change the .com to .ca in the URL and you will see the CAD listings: https://amzn.to/2tgS3eR

i dump my marimo bowl quite often (a week and a half-two weeks or so) and i find that if you do it that way, you dont really have to scrub slime out of the bowl :) however, i still get little nematodes (aka round worms) and they drive me up a wall, because i have a really bad phobia of parasites/worm-like organisms. any idea of how i can get rid of my nematodes for good?

These are called detritus and they are simply found in unbalanced water conditions or poor quality water. I’d clean the gravel in the tank really well. However, with all live things, avoid using dish soap as it removes healthy bacteria that fix nitrates and nitrites that, in turn, fuel your plant. :)

Goldfish are pond fish and can live up to 10 years, that being said, they grow far too large for a bowl. Moss balls are really great for betta fish bowls though, as moss balls act as a natural filter, always pulling water in and out and making a small current. Betta fish are known to really love them.

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